Change speed mechanism



Oct. 26, 1937. H KOHN l 2,097,283

' CHANGE SPEED MEGHANISM 'Filed Dec. 26, 195s @Tram/ey.

Patented Oct. 26, 1937 UNITED STATES CHANGE SPEED MECHANISM Hans Kohn,Stoetten Oberamt Geislingen, near Stuttgart, Germany ApplicationDecember 26, 1935, Serial No. 56,143 In Germany January 2, 1935 1sclaims.

This invention relates to a change speed gear with an infinitelyvariable transmission ratio between the driving and driven shafts. Theobj ct of the invention is to provide such a gear in w ch 5 the powertransmitting parts are all positively connected together so that' slipand consequent friction between power transmitting parts do not occur.All toothed wheels are to remain permanentlv in engagement with eachother during l0 alteration of the transmission ratio and thetransmission of power is to take place without the use of reciprocatingparts.

The gear in accordance with the invention comprises essentially adiierential gear and an L epicycllc gear connected to it. By suitablecontrol of the latter, the transmission ratio can be constantly altered.This transmission ratio is determined by the relation between the rateof rotation of the part of 'the differential connected to' the drive,that is to say, the driving part of theI differential, to that of thedriven part of the differential connected to the driven part of thegear. The rotation of the driven part of the differential can be alteredat will through the agency of the epicyclic gear, with the result thatthe rotation of the driven part of the differential and that of thethird, controlling part of the diierential can be continuously altered.The latter part which belongs to the epicyclic gear, will be referred toin what follows as the connecting part.

In order to alter the rate of rotation of this connecting part at will,the rolling movement of theywheel which is in engagement with theconnecting part, that is to say, the rate of rotation of its carrier,can be constantly altered by suitable means.

In order to be able to provide a suitable abutment or reaction point inthe carrier for theregulation, inspite of the rotation of all the powertransmitting parts, the driving member is connected not. only to thedifferential gear but also vto the epicyclic gear. TheI chain ofcontrolling parts, that is to say, the parts which serve for alterationof the transmission ratio, is also thus connected at two points,preferably at its two ends, to the drive.

A further object of the invention is to make it vpossible to alter therate of rotation of the carrier with the least possible expenditure of50 power and, in particular, so that only torques of suitably small sizehave to be overcome or even so that the torques acting on the carrierare fully balanced. With partial or complete compensation or balancingof 4these torques, a further gear 55 or gear member is mounted on thecarrier; this exerts a torque at its bearing point which acts againstthe torque transmitted to the carrier through the rolling wheel. Thisadditional gear member, which can be constructed as a toothed or camwheel, engages with the rolling wheel preferably diametrically oppositethe point of engagement of the pinion belonging to the connecting part.If the bearing of this gear member is displaceable relatively to thecarrier, the two oppositely acting torques on the carrier can be fullybalanced or, if desired, one canbe made to exceed the otherby only 'asmall amount.

A suitable form of construction is obtained by connecting the drive tothe planet support of the diierential gear, connecting one sun-wheel ofthe diierential gear to the driven shaft and the other sun-wheel to theconnecting part leading to the epicyclic gear. In this way, the relativemovements between the parts decreases as the rate of rotation of thedriven shaft increases and nally, with the top gear ratio, there is nosuch relative movement at all so that the gear is the equivalent of asolid shaft. When running light, the connecting part runs twice as fastas the driving shaft. It the carrier is set in rotation or its rate ofrotation is increased, the rate of -rotation of the connecting partdecreases and the rate of rotation of the driven sun-wheel of thedifferential increases correspondingly. The transmission ratio of theepicyclic gear is, for this purpose, preferably chosen as 1 is to 2.

As already mentioned, the equalization of the torques on the carriercan, as desired, be made more or less complete. If this is carried outso that there is a small resultant torque on the carrier in thedirection of the drive, the`transmission ratio can easily be altered bycoupling the carrier yieldingly with the driven shaft. In this case, thecarrier is urged constantlysomewhat in advance of the driven member. Ifthe coupling between the carrier and the driven shaft is somewhatreleased, owing to this tendency of the car- 4 rier to rotate faster,the rotation of the slower part is somewhat slackened, whereupon thedriven sun-wheel of the differential rotates more rapidly. When thedesired increase in the transmission ratio is obtained, the driven shaftneed only again -be coupled to the carrier in order that thattransmission ratio may be permanently maintained.

If the rate of rotation of the carrier is to be altered by a specialadjustable drive, it is neces' saryto adjust the parts of the drivemounted on the carrier so that their torques acting in opposltion toeach other are equalized or so that a weak resisting torque is exertedon the carrier.

A few of the many possible forms of construction in accordance withtheinvention are illustrated by way of example in the drawing, in

which I Figure 1 is an axial section through one form of construction ofthe gear as a whole.

Figures 2 and 3 are partialsections on the is integrally formed with apinion 44 to which it is connected by a sleeve 43 loosely mounted on ashaft 41". The parts 42, 43,44 will bereferred to as the connectingmember". An internally toothed wheel which is mounted freely in themember 41 and having an axis of rotation B-B engages withthe pinion 44.The part 41 .will be referred to as ,the planet carrier 'or carrier"in'contradistinction to part 35 referred to as planet support. Carrier41 isjournalled in the driving shaft at 41' and in the driven shaft 33by means of shaft 41" to which itis secured so that its axisof rotationA-A coincides with that of the driving and driven shafts. The connectingmember 42, 43., 44 is journalled in the bearing'member 41. The distanceofthe axis B-B from the axis A--A is fixed.

When the carrier 41 rotates about4 the axis A-A, the wheel 45 rolls onthe pinionV 44 in addition to rotating about the axis B- B. Theconnection between the wheel 45 and the driving shaft is as follows. 'Awheel 43, connected to the driving' shaft 33 through a universal c'ou.pling 43. is mounted torotate on a pin 41"' on the carrier 41. 'The axisC-C of this pin, the axis A-A and the axis -lit-B all lie on a commondiameter-of the carrier 41. -The wheel`43 has teeth 43' (Figure 2).,which engage in corresponding spaces 45' in thewheel 45. The number ofteeth 43-equals the number of spaces 45" and can. -be of any desiredmagnitude. At any time, there is, practically speaking, only one tooth43 bearing on the flank. of lthe space 45' and at fa point substantiallydiametrically. opposite to the point of engagement of the pinion 4 4with the wheel 45. (There are actually two teeth in engage- Amentfor ashort time when one tooth is Vabout to lose engagement' and thefollowing tooth'is about to engage.) 'Ihe transmission ratio of the gearvaries with variation inthe rate -of rotation of the bearing member 41.Whenidling, that is to say, when the driven parts 33, 4I are at rest,the planet wheels 43 roll as they rotate -about the stationary sun-wheel4i.v The sun-wheel 42 is thus rotated at double the speed of the planetsupport or the driving shaft 33. (Whateler the transmission ratio maybe, the. sum-of the rate of rotation of-the-sun-wheels 4|,v42 is alwaystwice as large as the rate of rotatiorrofY the driving shaft.) If, as ispreferable, the gear.

ratio of the wheels u, as is asfi a to 2, the large wheel 45, at noload, rotates half asfast about its axis B B as its pinion 44 rotatesabout lthe axis A- A, so that it has the same rate otrotation as the.planet support-35 and the Vdriving shaft 33.

The driven han nv u set in meson or as -aoavgias speed is increased as aconsequence of a decrease in the speed of the sun-wheel 42, or of the.con' the driving parts 35, 36, the rate of rotation of the drivensun-wheel 4I increases in the same ratio as the rate of rotation of thesun-wheel 42 is lowered. 'Ihis lowering of the rate of rotation of theconnecting member 42, 43, 44 isbrought about by causing the carrier 41to rotate about vits axis A--A in the same direction as the drivingshaft. 'Ihis causes the wheel 45 .to roll roundthe pinion 44 in thesenseof rotation of the driving shaft. 'I'he rate of rotation of theconnectingl member 44, 43, 42 is lowered in accordance with the rate atwhich the wheel 45 -rolls round the pinion 44 and this leads Ato thewheel 4| and, therefore, the driven shaft 33, being set in motion orbeing rotated more quickly. The top gear ratio, that is to say,l thedirect drive, is obtained when the carrier 41 rotates at the samespeed'as the driving` parts '35, 31, 35,

43, 45. In this case, the connecting member 44, 43, 42 also, however,has the same. speed of lrotation as, therefore,`have the drivensun-wheel 4I and the driven shaft 33. It will be clear -that in thiscase, all partsof the gear are at rest relatively to each other. .Theyrotate about the shaft 33, 33 as a single member sothat friction wouldbe difilcult and would necessitate the application of a large force. Inorder to reduce this resisting torque to the desired extent, to overcomeit completely or substantially, the wheel 43 is journalled on the member41 and, indeed', in such a waythat'its axis C -C lies nearthe axis B-B,coincides with it or, as illustrated, lies on the side of it remote fromthe axis A-A. The wheel 43, which is directly connected to the drivingshaft 33, exerts a .torque on the carrier- 41 through its bearing pin41" which .acts in opposition to that produced by vthe wheel 4'4. "lhus,by suitable choice of the distance of the axes B-B and C-C from eachother, it is-po'ssible to make these two torquesequal to each other. Thebearing pin 41"- can advantageously be mountedin a slide 414' whichis'radially adjustable in the member 41(seeFisu re4).-

.If, asis illustrated in Figure 1, the pin 41"' is so arranged that ,itsaxis c c lies further from there will be a slight resultant torque inthe direction of the drive acting on the carrier 41. 'In

that case, the member 41 tendsto run somewhat the tion ratio can bealtered in a simple manner as follows: A disc vA having acircumferential groove 53 is keyed tothe shaft 41" of the carrier". Abolt 5I lispressed into'this groove by means of a spring Il', the boltbeing `mounted on the driven member 4I, 33. The bolt 5I holds thecarrier 41. so'that it cannot mn faster than the driven shaft 33.Ifffor: the purpose of increasing'the` traon ratio, the bolt 5I is largewheel 45 is thus caused to roll further-on the pinion 44 so/that theconnecting part 44, 43, 42, is rotated more slowly to that extent.Consequently, the rate of rotation of the driven part 4l, 38 increasesuntil the bolt 5l, by engagement in the groove'50, prevents this raisingof the transmission ratio.

The transmission ratio is automatically lowered to the extent to whichthe driven shaft 38 runs more slowly. This reduction in the transmissionratio can be effected in a simple manner and with the application ofsmall forces by reducing the rate of rotation of the approximatelybalanced carrier 41, by braking it, as illustrated. The disc 50 carriesa brake drum 5I!" comprising a Braking member 52 which can be operatedlfrom the outside in any desired fashion,

for example by means of the device 53. The bolt 5i and the brakingmember 52 are preferably alternately actuated by a common controllingdevice. l v

If the two driving parts and 48 mounted on the member 41 act on themember 41 in such 'a manner that their torques acting in oppositedirections are compensatory or so that a slight resisting'torque isexerted onthe member 41, the rate of rotation of the member 41 can beadjusted by a variable drive. The rate of rotation of the carrier 41 canbe adjusted by any suitable means. If the rate of rotation of thecarrier 4.1 is to be adjusted from the driving side instead of from thedriven side, its bearing 41' can, for example, be constructed in asimilar manner to that which is shown for the parts -53 in connectionwith the driven side.

Alternatively, as is shown in Figure 1, a toothed Wheel 415 on thecarrier`41 can be caused to engage with a pinion 60, the spindle 60' ofwhich passes through the casing 31 and has fixed to it outside thecasing a pinion '6 I of the same size as the' pinion 60. A toothed wheel62 mounted to rotate on the driving shaft 36 engages with this pinion5l. Its rate of rotation can be varied in any desired manner. yIn thisway, the drive 36 and the carrier 41 can rotate independently of eachother so that the pinions 60, 6I carry out corresponding `rollingmovements relatively to their toothed wheels 415 and 62 and,nevertheless, the carrier 41 arranged within the casing 31 can have itsspeed of rotation regulated as desired from the outside.

1. A change-speed mechanism comprising a driving shaft, a driven shaft,adiiferential gear positively connected to said driving shaft and saiddriven shaft, a toothed wheel having a fixed axis of rotation positivelyconnected to said-differential gear, a toothed wheel adapted torollround said rst mentioned toothed wheel, a carrie'r for said secondmentioned toothed wheel, a rotary member mounted on said carrier andserving to connect said second mentioned toothed wheel to said drivingshaft, said rotary member being in driving engagement with said secondmentioned toothed wheel at a point substantially diametrically oppositethe point of engagement of said toothed wheels and means for varying therate-ef. .rotation of said carrier.

claim l comprising means for braking the movement of said carrier.

4. A change-speed mechanism as claimed in claim 1 in which said meansfor varying the rate of rotation of said carrier comprise gear teeth onsaid carrier, a gear wheel mounted for rotation on said driving shaftand gearing mounted for rotation with said driving shaft and about theaxis of said driving shaft and engaging with said gear teeth and saidgear wheel.

5. A change-speed mechanism, comprising a driving shaft, Ya driven shaftcoaxial with said driving shaft, a differential gear having a pair ofsun wheels coaxial with said driven shaft, one of said sun wheelsbeingpositively connected to said driven shaft, a planet Wheel and acarrier for said planet wheel positively connected to said drivingshaft, aninternally toothed gear wheel driven by said driving shaftabout an axis parallel tobut displaced from the axis of rotation of saidshaft, an externally toothed wheel positively connected to that of saidsun wheels not connected to said driven shaft and meshing with saidinternally toothed wheel and means for rotating said internally toothedWheel aboutthe axis of rotation of said driving shaft.

6. A change-speed mechanism comprisinga driving shaft, an internallytoothed wheel adapted to be rotated about its own axis by said drivingshaft and about the axis of said driving shaft, an externally toothedwheel in permanent engagement with said internally toothed wheel anddisposed coaxially with said driving shaft, a Vdiffer- -ential gearhaving an input sun wheel positively connected to said externallytoothed wheel, an

voutput sun-wheel positively connected to said driven shaft and a planetwheel adapted to be `rotated about the axis of said sun wheel by saiddriving shaft, and means for varying the rate of rotation of saidinternally toothed wheel about the axis of said driving shaft.

. 7. In a change speed mechanism comprising a driving shaft, and adriven shaft, the combination of an epicyclic train arranged 4betweensaid shafts, and including a planet wheel, a sun wheel and a planetwheel carrier, said epicyclic train being of the type in which thetransmission ratio may be varied by varying the rate of rotation of itsplanet wheel carrier, with a rotary element meshing with said planetwheel and being supported for rotation on said planet wheel carrierwhereby the torque acting on said iplanet wheel carrier due to theinteraction of said sun wheel and said. planet wheel 'may be at leastpartially compensated by a torque acting on said planet wheel carrier inthe opposite sense through said rotary element.

8. In achange speed mechanism comprising a driving shaft, and a drivenshaft, the combination of an epicyclic train arranged between saidshafts, and including a planet wheel, a sun wheel `and a planet wheelcarrier, said epicyclic train being of the type in which thetransmission ratio may be varied by varying the rate of rotation of itsplanet wheel carrier, with a rotary element meshing with said planetwheel andl mounted for rotation on said planet wheel carrierexcentrical'- ly with respect to the axis of said driving shaft, saidrotary'element being in driving connection with said driving shaft.

9. In a. change speed mechanism comprising a driving shaft, and a drivenshaft, the combination of an epicyclic train arranged between saidshafts, and including a planet wheel, a sun wheel, and a planet wheelcarrier, said epicyclic train being of the type in which the.transmission ratio may be varied by varying the rate of rotation of itsplanet wheel carrier, with a rotary element meshing with said planetwheel and supported for rotation on said planet wheel carrier,'the axisf said rotary element, of said planet wheel, and

, torque acting on said planet 4wheel carrier in the opposite sensethrough said rotary element.

10. In a change speed mechanism comprising a driving shaft, and a drivenshaft, the combination of an epicyclic train arranged between saidshafts, and including a planet wheel, a sun wheel and a planet wheelcarrier, said epicyclic 'train beingof the type in which thetransmission ratio may be varied by varying the rate of rotation of itsplanet wheel carrier, with a rotary element meshing with said planetwheel and mounted for rotation on said planet wheel carrier'excentrically with respect to the axis of said driving shaft, saidrotary element being in driving connection with said driving shaft, theaxes of said rotary element, of saidplanet wheel, and of said drivingshaft lying on a lcommon diameter 'of the planet wheel carrier;

1 1. In a change speed mechanism comprising a driving shaft, and.drivenshaft, the combination of an epicyclic train arranged between saidshafts, and including a planet wheel, a sun wheel and a planet wheelcarrier,said epicyclic `train being of the type in which thetransmission ratio may be varied by varying' the rate of rotation of itsplanet wheelcarrier, with a rotary element meshing with said planetwheel and supported for rotation on said planet wheel carrier, the axisof said rotary element being displaceable parallel to itself, the axisof said rotary element, of said planet wheel, and of. said driving shaftlying on a common diameter of the planet wheel carrier, whereby thetorque acting on said planet wheel carrier due to the interaction ofsaid sun wheel and said planet wheel may be at least partially`compensated by a torque acting on said planet wheel carrier in theopposite sense through said rotary element.

12. In a change speed mechanism comprising a driving shaft, and a drivenshaft, the combination of an epicyclic train arranged between saidshafts, and including a planet wheel, a s'un wheel and a planet wheelcarrier, said epicyclic train being of the type in which thetransmission ratio may be varied dby varying the rate of rotation of itsplanet wheel carrier, with a rotary element supported for rotation onsaid planet wheel carrier and meshing with said planet wheel at a pointwhich is substantially diametrically opposite to the point of engagementof said planet wheel and said sun wheel whereby the torque acting onsaid planet wheel carrier. due to the interaction Aof said sun wheel andsaid planetwheel may be at least partially compensated by a torqueacting on said planet wheel carrier in'the opposite sense through saidrotary element.

13. In a change speed mechanism comprising a driving shaft, and a drivenshaft, the combination of an epicyclic train arranged between said eterof the planet wheel carrier, and the axis of said rotary element beingarranged at the same side of and at a slightly greater distance from theaxis of saidy driving shaft than the axis of said planet wheel, wherebysaid planet wheel carrier may be constantly urged somewhat in advance ofsaid driven shaft by a torque acting on said planet wheel carrierthrough said rotary element.

14. In a changespeed mechanism comprising a driving shaft, and a drivenshaft, the combination of an epicyclic train arranged between saidshafts, and including a planet wheel, a sun wheel and a planet'wheelcarrier, said epicyclic train being of the type in which thetransmission ratio may be varied by varying the rate of rotation of itsplanet wheel carrier, with means in engagement with said planet wheelcarrier for at least partially compensating the -torque acting on saidplanet wheel carrier due to the interaction of said sun wheel and saidplanet wheel, and means for yieldingly coupling said planet wheelcarrier with said driven shaft. A

15. In a change lspeed mechanism comprising a driving shaft, and adriven shaft, the combination of an epicyclic train arranged betweensaid shafts, and including a planet wheel, a. sun wheel and a planetwheel carrier, said epicyclic train being of the type in which thetransmission ratio may be varied by varying .the rateof rotation of itsplanet wheel carrier, with means in engagement with' said planet wheelcarrier for at least partially compensating the torque acting on saidplanet Wheel carrier due to the interaction of said sun wheel and saidplanet wheel, a disengageable, yielding coupling means between saidplanet wheel carrier and said driven shaft, means for braking saidplanet wheel carrier, and operable means for alternatively actuatingsaid coupling means and said braking means.

16. In a change-speed mechanism comprising a driving shaft, .and adriven shaft, the combination of an epicyclic train arranged betweensaid Shafts, and including a planet wheel, a sun wheel and a planetwheel carrier, gear teeth on said planet wheel carrier, -a gear wheelrotatably mounted on said drivingshaft, planetary wheels for which saidgear teeth and said gear wheel form thesun wheels, said planetary wheelsbeing connected together with a common axis and being adapted to bedriven round the axis of the driving shaft by the latter, and means inengagement with said planet wheel carrier for at least partiallycompensating the torque acting on said planet wheel carrier due -to theinteraction of said first mentioned sun wheel and said planet wheel.

- HANS KOHN.

